1. Field of the Invention
The present invention relates to a portable computer with negligible noise level, and in particular to a portable computer utilizing a system controlling method, determining appropriate fan driving voltage and system efficiency according to surrounding acoustic level.
2. Description of the Related Art
As processing speeds of central processor unit (CPU), a chipset, a graphics processing unit (GPU), an accelerated graphics port (AGP), or dynamic random access memory (DRAM) in an electronic device such as a notebook have increased considerably, and such elements are disposed on different areas of a motherboard, energy density has increased accordingly. Due to such designs, a fan controlling system is required to control heat dissipation in the notebook.
FIG. 1 is a flowchart of a conventional fan controlling system of a notebook. As the notebook is started (step S101), the heat dissipating fan is operated at a predetermined speed to dissipate heat from the system (step S102). During operation, the temperature of the CPU is intermittently detected (step S103), and the system determines whether the CPU temperature is higher than a predetermined allowable temperature (step S104). When the CPU temperature is higher than the predetermined allowable temperature, the speed of fan is increased (step S105) to increase airflow, thereby facilitating heat dissipation. After a certain period of time, the system detects the CPU temperature again, checking whether the CPU temperature decreases below the allowable temperature (step S106) If the CPU temperature is less than the allowable temperature in step S106, the fan is kept at the same operating speed. If the CPU temperature is higher than the allowable temperature, the fan speed is increased, and the controlling process repeats.
With the same number of fans, airflow produced by the fans attempts to carry heat away from the system. In order to increase airflow, the speeds of fans must be increased by raising the driving voltage accordingly. However, as the speed of fan is increased, noise is inevitably produced thereafter. Thus, as heat is produced and temperature increases due to multiple elements in a system, to dissipate excess heat, the driving voltage must be increased to increase speed of fans, thereby producing enough airflow to carry excess heat away from the system. FIGS. 2A, 2B, 2C, 2D are plots of speed, noise level, airflow of the fan and temperature versus voltage. Thus, in a conventional fan controlling system, heat dissipation must be achieved at the cost of system noise level.
Using the fan controlling method mentioned above, when heat of the system is increased, it can be dissipated by increasing fan driving voltage, fan speed, and airflow, finally reducing system temperature. However, noise is followed by such a high fan speed, making users feel uncomfortable. Thus, there remains a need for a system that can increase heat dissipation without producing unpleasing noise.